Goals of this project are to improve clinical laboratory methods for diagnosis of disease. Studies include analysis of clinical laboratory practices, analysis of the accuracy of laboratory tests, and development of new tests and testing technologies. The major efforts over the past year have been to continue work on the effect of blood collection tubes on assays, to characterize urinary proteins of potential diagnostic significance, and to evaluate the distribution of homocysteine between different plasma protein fractions. 1) Analyses of effects of blood collection tubes found complex interactions with the analysis of free fatty acids probably due to modification of the specimen rather than direct interaction with the assay. These efforts help identify optimal collection procedures and tubes for collection of specimens for free fatty acid analysis and point to new mechanisms by which laboratory results may be affected by collection tubes. 2) Studies of urinary proteins have focused mainly on analysis of urinary albumin which serves as one of the most widely used markers for early glomerular injury. Our laboratory has examined how clinical assays measure modified forms of albumin that may occur in urine and have undertaken efforts to characterize the modified forms of albumin in urine. These efforts are expected to contribute to better clinical application and interpretation of urinary albumin measurements for the detection of kidney injury. 3) Plasma homocysteine has been of great interest as a potential risk factor for cardiovascular disease and thrombosis. We have examined the linkage of homocysteine to plasma proteins via disulfide bonds. Our analyses may subdivide the total homocysteine content into different subfractions bound to different proteins, and we have examined the differential exchange of homocysteine bound to different protein fractions. These studies seek to understand the interactions of homocysteine with plasma proteins and to identify subfractions of homocysteine that may serve as better indicators of cardiovascular disease.